Step 6: Have a Supernatural Minifig with a Cliché that allows for Summoning. Examples include D&D style Wizards, Druids and Clerics, JRPG characters, or sockpuppeting forum trolls.

Step 7: Spend one of their SN Dice to summon the Diemon. The Diemon will have the base stats assed in the Diemon section, and the die spent will stay spent until the Diemon is killed or unsummoned. The Diemon may be further augmented with SN Dice as normal, using the SN Dice rules.

Step 8: Assuming an unaugmented, basic Diemon, on their turn they may use their die to either move, or use an Action. Diemon don't seem to have a natural attack assed, so I would guess that either they are meant not to, and must use picked up weapons; or are meant to be treated as Vermin, and have a (Use:1, Damage:1) attack.

That's right. Diemons don't have any built-in attack, although 4pions can do 1d4 Fire damage just by touching things, 6creants are big enough to pick up weapons and use them, and 10amytes can blow up like bombs. But most of the time, if you want to make attacks with diemons, you have to augment them with more SN dice. Otherwise they're mostly just good for sending around on minor errands (d8vians are good for flying around and retrieving objects, for instance) and distracting people.

It might be funny to give diemons the ability to cast themselves as SN dice once they reach a target, but that might be overpowering them. Hard to say.